R help - Mar 2010 - add a header to a forest plot (metafor)

Dear R-community,

 

I'm currently trying to assemble a forest plot using the "forest"
function
from package "metaphor".

Works well. Even the regular "main"-argument works for adding a title
to the
graph. 

 

However, I would like to add one top row which explains the nature of the
columns. Very much like the usual header in spreadsheet programs. 

For example: "Study"   "Sample"   "Sample Size"  
"Estimated Effect Size"
"CI 95%".

 

I tried to add "axis(3)", but apparently the forest plot isn't
that kind of
graphic.

 

Does anyone have any idea? 

 

Cheerio

Sebastian

 


	[[alternative HTML version deleted]]

Hi Sebastian,

Here is an example showing a forest plot with some column headings:

########################################################################

library(metafor)

data(dat.bcg)
dat <- dat.bcg

res <- rma(ai=tpos, bi=tneg, ci=cpos, di=cneg, data=dat,
measure="RR")

windows(width=6.5, height=4.0, pointsize=10)
par(mar=c(4,0,4,0))
forest(res, slab=paste(dat$author, ", ", dat$year, sep=""),
       xlim=c(-16,6), at=log(c(.05,.25,1,4)), atransf=exp,
       ilab=cbind(dat$tpos, dat$tneg, dat$cpos, dat$cneg),
       ilab.xpos=c(-9.5,-8,-6,-4.5), cex=.8, ylim=c(-1.5,16), efac=1.8)
text(c(-9.5,-8,-6,-4.5), 14.7, c("TB+", "TB-",
"TB+", "TB-"),   font=2, cex=.8)
text(c(-8.75,-5.25),     15.7, c("Vaccinated", "Control"),  
font=2, cex=.8)
text(-16,                14.7, "Author(s) and Year",     pos=4,
font=2, cex=.8)
text(6,                  14.7, "Relative Risk [95% CI]", pos=2,
font=2, cex=.8)
title("Figure 1: Forest Plot of the BCG Vaccine Data")

########################################################################

So, just use the text() function to add those column headings. With the ilab and
ilab.xpos arguments, you can add the information for those columns to the plot.

I hope the example helps!

Best,

--
Wolfgang Viechtbauer                        http://www.wvbauer.com/
Department of Methodology and Statistics    Tel: +31 (0)43 388-2277
School for Public Health and Primary Care   Office Location:
Maastricht University, P.O. Box 616         Room B2.01 (second floor)
6200 MD Maastricht, The Netherlands         Debyeplein 1 (Randwyck)


----Original Message----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Sebastian Stegmann Sent: Tuesday, March 02, 2010 18:36
To: r-help at r-project.org
Subject: [R] add a header to a forest plot (metafor)
> Dear R-community,
>
> I'm currently trying to assemble a forest plot using the
"forest"
> function from package "metaphor".
>
> Works well. Even the regular "main"-argument works for adding a
title to
> the graph.
>
> However, I would like to add one top row which explains the nature of the
> columns. Very much like the usual header in spreadsheet programs.
>
> For example: "Study"   "Sample"   "Sample
Size"   "Estimated Effect Size"
> "CI 95%".
>
> I tried to add "axis(3)", but apparently the forest plot
isn't that kind
> of graphic.
>
> Does anyone have any idea?
>
> Cheerio
>
> Sebastian
>
>
>       [[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.